REVIEW OF THE PROBLEMS INVOLVED IN USING ENZYMES IN BLOOD-GROUP SEROLOGY - PROVISION OF FREEZE-DRIED ICSH ISBT PROTEASE ENZYME AND ANTI-D REFERENCE-STANDARDS/

Proteolytic enzyme preparations and techniques used routinely in blood group serology for the detection of atypical patient antibodies prior to transfusion vary widely and are often poorly standardised. Recent advances have been made in the use of biochemical methods to standardi se and stabilise the potency of the enzyme preparations used. A joint working party of the International Council for Standardization in Haem atology (ICSH) and the International Society of Blood Transfusion (ISB T) has investigated possibilities for the provision of standards for t he protease preparations and techniques. The specification for these s tandards was that the performance of enzyme reference preparation in t he reference technique should be of equivalent sensitivity to the ICSH /ISBT LISS spin indirect antiglobulin test using a titration series of a reference weak anti-D, and be free from false-positive reactions. T he working party circulated materials for evaluation in inter-laborato ry trials, followed by a laboratory workshop meeting to achieve agreem ent on the specification for reference materials and methods. Referenc e freeze-dried papain at 0.6 azoalbumin units and weak anti-D preparat ions (91/562) have been prepared and validated to meet these specifica tions. The performance of a test enzyme preparation in the technique f or which it is recommended for use should be at least equal to that of the reference papain preparation, by the reference two-stage techniqu e in terms of sensitivity, using a titration series of the reference a nti-D, and freedom from false-positive reactions, using six fresh iner t sera. The reference papain and weak anti-D can also be used to calib rate the level of proteolytic activity required in other procedures in blood group serology, such as new technology methods for antibody det ection, and automated and microplate cell grouping procedures. These p reparations and an agreed method for their use are now available from listed centres as ICSH/ISBT and Food and Drug Administration reference materials.